12.13.3 Diagnostic information and procedures 

12.13.3.1 Common Defects Example and Treatment for Paint Surface 

Notes: 

Making the box in the table black indicates the treatment for this defect. 

Description Formation 

causes 

Treatment 

Powder 

The paint film is eroded strongly. Such as strong 
ultraviolet ray, paint ratio during construction is 
wrong. 

Coating has low resistance to sun and bad weather. 

Vehicle cleaning is not regular or thorough. 

Incorrect choice of cleaning agents or too coarse 
polishing wax. 

1.   Polishing Treatment. □ 

2.  Conventional grind and polishing 

treatment. □ 

3. 

 Treated with deep grinding, 

polishing and modification. □ 

4. Partial 

paint 

repair. 

■ 

Plastic Paint 
Peeling 

Poor adhesion between the coating and the substrate 
or outer coating is too hard relative to under coating. 

Coating is too thick or erosions are caused by water 
vapor, acid and alkali in the air. 

Under coating is treated incorrectly; there are pinholes 
and defects in the outer paint. 

1. Polishing 

Treatment. 

□ 

2.  Conventional grind and polishing 

treatment. □ 

3. Treated with deep grinding, polishing 

and modification. □ 

4. Partial 

paint 

repair. 

■ 

Cracking 

Primer is inadequately stirred prior to spraying. 

Base coating is too thick. 

Middle coating is too thick. 

1. Polishing 

Treatment. 

□ 

2.  Conventional grind and polishing 

treatment. □ 

3. 

 Treated with deep grinding, 

polishing and modification. □ 

4. Partial 

paint 

repair. 

■ 

Bird 
Droppings 
Erosion 

1. Erosion by bird manure dropping. 

1.  Polishing treatment (mild erosion). 

■ 

2.  Conventional grind and polishing 

treatment (medium erosion). ■ 

3. Treated with deep grinding, polishing 

and modification. □ 

4. Partial paint repair (severe 

erosion). ■ 

Scratch 

Film with low hardness. 

Scratch caused by hard objects. 

1. Polishing  treatment  (minor 

scratches). ■ 

2.  Conventional grind and polishing 

treatment (thick scarring). ■ 

3. 

 Treated with deep grinding, 

polishing and modification. □ 

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4.  Partial paint repair (scratched). ■ 

Corrosion 

Thin film of edges. 

Corrosion caused by hurt generated by knocks. 

Acid and alkali erosion. 

1. Polishing 

Treatment. 

□ 

2.   Conventional grind and polishing 

treatment. □ 

3. 

 Treated with deep grinding, 

polishing and modification. □ 

4.  Partial paint repair (serious rusted 

metals need to be repaired before 
painting). ■ 

Paint Peeling 

Poor adhesion between the coating and the substrate 
or outer coating is too hard relative to under coating. 

Coating is too thick or erosions are caused by water 
vapor, acid and alkali in the air. 

3. Under coating is treated incorrectly; there are 
pinholes and defects in the outer paint. 

1. Polishing 

Treatment. 

□ 

2.  Conventional grind and polishing 

treatment. □ 

3. 

 Treated with deep grinding, 

polishing and modification. □ 

4.  Partial paint repair (serious rusted 

metals need to be repaired before 
painting). ■ 

Acid Rain 
Erosion 

1. Acid Rain Erosion 

1.  Polishing treatment (mild erosion). 

■ 

2.   Conventional grind and polishing 

treatment (medium erosion). ■ 

3. 

 Treated with deep grinding, 

polishing and modification. □ 

4.  Partial paint repair(severe erosion). 

■ 

Gloss 

1.  Film is eroded by the acid, alkali, electric arc, 
sea water and other strong corrosive salty spray. 

Incorrect maintenance methods in harsh conditions. 

3. Poor paint durability. 

4. Incorrect paint mixture ratio leads to paint 
durability deterioration. 

1.  Polishing treatment (mild loss of 

light). ■ 

2.  Conventional grind and polishing 

treatment (moderate loss of light). 
■ 

3. 

 Treated with deep grinding, 

polishing and modification. □ 

4.  Partial paint repair (severe loss of 

light). ■ 

Bubbling 

When film is exposed to a humid environment for a 
long period, water vapor will infiltrate into paint film, 
and water and gas bubbling will be generated when 
temperature rises. 

Substrate is corroded by infiltrated materials. 

Gasoline, acid, alkali and other erosion for film. 

1.   Polishing Treatment. □ 

2.   Conventional grind and polishing 

treatment. □ 

3. 

 Treated with deep grinding, 

polishing and modification. □ 

4.  Partial paint repair (serious rusted 

metals need to be repaired before 
painting). ■ 

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12.13.4 Removal and installation 

12.13.4.1 Common Coating Film Defect Treatment Process Example 

1.  Before polishing, clean the surface to be polished 

with degreasing materials. 

 

NL12-1000b

2.  Firstly fully soak a sponge and squeeze excessive 

water. 

3.  Apply a small amount of polishing wax to the 

surface and adjust the polishing machine speed. 

 

NL12-1001b

4.  Put the wool ball onto the surface, turn on the 

machine with a speed at 2,500-3,000 r/ min. 
Then, slightly press for 3-5s for polishing 
treatment. 

Notes: 

During operation, keep the machine stable and move 
gently. Do not operate too long to avoid overheating, 
as the paint will be damaged by the heat. 

5.  Use a cleaning cloth to wipe the excessive wax. 

 

NL12-1002b

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12.13.4.2 Conventional Grind and Polishing Treatment Process Example 

1.  Before polishing, clean the surface to be polished 

with degreasing materials. 

 

NL12-1000b

2.  Apply an appropriate amount of polishing wax to 

the surface and adjust the polishing machine 
speed. 

 

NL12-1003b

3.  Put the wool ball onto the surface, turn on the 
machine with a speed at 2,500-3,000 r/ min. 

Notes: 

During operation, keep the machine stable and move 
gently. Do not polish too long. Keep the polishing 
time as short as possible, and the polishing area as 
small as possible. 

4. Wet sufficiently the sponge and remove excessive 
moisture by compressing it. Apply a small amount of 
polishing wax to the surface to be polished and start 
the engine to a RPM of 2,500-3,000r/min after 
pressing the sponge to the surface to be polished. 
Then, slightly press for 3-5s for polishing treatment. 

Notes: 

During operation, keep the machine stable and move 
gently. Do not operate too long to avoid overheating, 
as the paint will be damaged by the heat. 

NL12-1004b

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